When the mob has a problems with rats, defense lawyer Gerald McMahon handles the it.

“No one does rats like I do,” McMahon told The New York Post. “My specialty is cross-examining rats. I have good instincts.”

The 65-year-old Irish American lawyer charges $800 an hour and uses "a combination of street smarts and textbook psychology."

Last July, McMahon helped helped reputed Colombo associate Francis “B.F” Guerra beat double murder, extortion and assault charges.

During the trial, he targeted five rats, including former Colombo capo Anthony “Big Anthony” Russo, whom he taunted for turning into a rat in order to stay out of a jail to be with his girlfriend Mitzi Medina.

The goal, said McMahon, was to let the jury see the “real” Russo — “big, fat, stupid and thuggish.”

Other rats, such as former Colombo capo Reynold Maragni, got a different treatment. McMahon says he fed Maragni's ego and let him dig his own grave. He got Maragni to admit that he was collecting loan-shark money after agreeing to cooperate with the FBI.

“With juries, you just have to give them a good reason to go where you want them to go, and they will find a way in the evidence,” he said.

He said many juries hate rats.

McMahon's father was federal prosecutor Daniel F McMahon, who went after Jimmy Hoffa in 1957.

Before becoming a lawyer, McMahon served in Vietnam, drove a cab, and worked as an actor in the Wisconsin troupe Theatre X.

“Some nights when I was on stage, I could literally feel that if I raised an eyebrow, the audience would react,” he said, recalling his turn as Willy Loman in “Death of a Salesman.”

“That’s what it’s like in the courtroom. They like a show.”